The present invention relates generally to the preparation of a water-impervious concrete structure that is also resistant to biological contamination. The colloidal sealant compositions of the present invention are preferably employed along with a topcoat composition such as an epoxy coating, a urethane coating or a polyurea coating. The colloidal sealant compositions of the present invention are distributed onto the concrete structure at least twenty-four to forty-eight hours before the application of the topcoat composition. If the topcoat is semi-permeable, then any biocidal material in the colloidal sealant composition can percolate to the top of the concrete structure and be effective against surface contamination by unwanted biologics such as molds, fungus, microbes and the like. Alternatively, with a nonpermeable topcoat, the biocidal material remains in a reservoir area located between the topcoat and the upper regions of the colloidal sealant composition.
A major cause of deterioration of concrete highways, bridge decks, parking garages, streets, airport runways, parking lots, sidewalks, driveways and the like is corrosion of reinforcing steel caused by chlorides from de-icing salt, airborne ocean spray and the like. Steel can expand as it rusts and deteriorates, thus causing the concrete to crack and fracture. These problems are overcome by the use of the colloidal sealant composition of the present invention, the composition actually becoming a part of the concrete structure upon gelling. The gelled colloidal sealant composition has the ability to drive chloride ion out of the cement structure. Even deeply penetrating chloride ion is ultimately pushed into the reservoir area created by the colloidal gel.
U.S. Pat. No. 6,869,256, issued to Greenwood et al, discloses a method for sealing rock or soil. A sealing composition is employed. The sealing composition contains a silica sol and at least one gelling agent. The gelling agent is selected from the group consisting of potassium chloride, sodium chloride, calcium chloride, magnesium chloride, magnesium nitrate, magnesium sulfate and mixtures thereof.
U.S. Pat. No. 6,209,357, issued to Bhandarkar et al, discloses a process for fabricating a silica body. The process comprises the steps of: adding a tetraalkylammonium hydroxide as a stabilizing agent to a silica dispersion, allowing the dispersion to age, adjusting the isoelectric point of the silica to about 9.0 or higher by addition of a compound such as an amine, inducing gelation of the dispersion into a gel body, and drying the gel body to remove water.
U.S. Pat. No. 5,925,416, issued to Akstinat et al, relates to a method for aftertreating surfaces of cured and non-cured binder suspensions. A colloid solution coating is applied to the surfaces. The colloidal solution is selected from the group consisting of oxides, hydroxides, oxihydrates and heteropolyacids of metals and nonmetals. Gel formation is induced after the coating is applied.
U.S. Pat. No. 5,744,239, issued to Buccellato et al, relates to a pavement marking system containing at least one antimicrobial agent.
U.S. Pat. No. 5,043,019, issued to Chervenak et al, relates to a composition useful as a sealant or coating for concrete block walls. The composition contains water soluble silicate, water, fibers, clay and limestone.
U.S. Pat. No. 4,207,115, issued to Boehme et al, discloses a method of obtaining a finished concrete structure having a water-impervious surface. A composition containing at least one glyceryl-fatty acid ester and a paraffin wax material is added to a wet hydraulic Portland cement slurry to form a mixture. The mixture is then allowed to hydrate and harden. After hardening, the concrete structure is heated to cause the wax material to melt and fill the capillary interstices in the structure.
The above-cited references, taken either individually or in combination, do not anticipate the present invention. There is no reference to a colloidal sealant composition that forms a water-impermeable gel, the composition containing a biocide. Said composition contains no alkali or alkaline earth elements, and contains no organic functionality.